[linux-lvm] old md-partitions to pvs

Mika Länsirinne Mika.Lansirinne at iki.fi
Thu Jul 29 16:41:53 UTC 2004

Hello all,

I converted couple of md partitions to pvs. The reason for this was to remove 
unnecessary md layer (raid0) and to replace it with striped lvs.

When I had stopped the md and edited the partition types in the partition 
tables (and rebooted) I tried to pvcreate those, but it told me that the 
device was not found.

I found out that vgscan or pvscan (or whatever which creates the .cache file) 
skipped those partitions because it thought they still are part of a md.

vgscan -vvv:
      Getting size of /dev/hda3
        Opened /dev/hda3
        /dev/hda3: Skipping md component device
        Closed /dev/hda3

and same for hdb3 also.

It seems that it founds MD_SB_MAGIC in those partitions 
(lib/filters/filter-md.c, lines 54-62).

I have my system working now by hand editing the /etc/lvm/.cache and to never 
vgscan again :). The pvcreate and all the rest works now.

The question is that how could I get rid of those md signatures? pvcreate 
obviously didn't do it, because it complained them in the first place. Of 
course, I could have wiped the whole partitions with zeros in the beginning 
(a long time), but now I already have a vg and several lvs and filesystems 
there. Maybe I should write the filesystems full temporarily? Would that even 

lvm tools version used is 2.00.15, kernel 2.6.7 and the system is fedora 2.


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